The challenge of anticipating and communicating the risk of volcanic eruptions to communities requires complex decision-making. Ecuador’s Cotopaxi Volcano and Indonesia’s Mount Agung are recent examples where the warning signs were present (small earthquakes, increasing gas emissions, and more), yet an eruption came much later than expected. Volcanic eruptions are therefore a double-edged sword that often creates a decision-making dilemma. While signs of volcanic activity[4] can provide adequate time for preparation and evacuation, the very same signs can also create conditions of extreme uncertainty, which can be exacerbated by piecemeal communication around eruption events.

1. While largely unpredictable, volcanic eruptions are devastating and can change the course of humanity.

Over the last 11,500 years, more than 1,500 major eruptions have occurred[6], with approximately 500 in the Pacific "Ring of Fire" alone. We don’t have to look far back in history to find examples of devastating volcanic eruptions. The instantaneous destruction of Pompeii by Mt. Vesuvius is perhaps the most oft-cited event, but a more devastating, less remembered event is the 1815 Mount Tambora eruption[7] in Indonesia. The "Pompeii of the East" claimed the lives of more than 70,000 people. Mt. Tambora’s ash fallout led to climate anomalies[8] throughout Europe and North America for years afterward, causing the century’s worst famine. Dozens more recent eruptions[9] have claimed tens of thousands of lives and caused billions of dollars in economic losses, including: El Chichon (Mexico); Nevada del Ruiz (Colombia); Mt. Pinatubo (Philippines); Mt. Etna (Italy); and Iceland’s Eyjafjallajökull[10].

2. Communicating risk for volcanic eruptions on a timely basis is not straightforward.

Though the science of volcanic eruption forecasting[11] has come a long way in recent decades, accurately predicting volcanic eruptions and communicating uncertainty to highly exposed communities is fraught with difficulties and can quickly become ineffective. For example, communities may risk not evacuating, or wait for clear communication that a volcano is likely to erupt when it’s already too late to evacuate. While volcanology offers a wide range of measurements that can indicate if and when an eruption will occur, timely decisions still need to be taken by experts regarding when to publicly sound the alarm.

Given that large-scale evacuations require tremendous resources and have ripple effects on economic activity, should governments err on the side of caution, or preparedness?

Although Italy’s dormant Vesuvius volcano has not erupted since 1944, satellite image of eruptions can contribute to disaster mapping at any time. Image credit: ESA[14]Deciding how to deal with risk[15] is an inherently political process, and our decisions have serious and lasting consequences, including for potential volcano eruptions. But informational complexity and compounding uncertainty should not dissuade us from taking action to ensure the safety and prosperity of communities. The way forward, among many possible courses of action, will not simply be discovered – it must be created.

To delve into these questions and others, the University of Plymouth, GFDRR, and the World Bank are hosting a dedicated session at the 2018 Understanding Risk Forum[19] in Mexico City on May 17, 2018. As we focus on the specter of volcanos, we will also consider how our discussion and conclusions might be of value to those faced with climate change uncertainty, rapid urbanization, and other concerns closely related to volcano risk.

We hope you will join the conversation with the session moderator, Professor Iain Stewart[20] either in Mexico City at UR2018[21] or via Twitter. Submit your questions ahead of the event by tweeting at @UnderstandRisk[22] using #URVolcanos[23] and we’ll answer them online and live during the session.